A quantitative magnetospheric model derived from spacecraft magnetometer data

摘要: A quantitative model of the external magnetospheric field has been derived by making least squares fits to magnetic measurements from four Imp satellites. The data set consists 12,616 vector averages over half-earth radii intervals between 4 and 17 RE, taken 451 satellite orbits 1966 1972. were fit a power series expansion in solar coordinates wind-dipole tilt angle, thus contains effects seasonal north-south asymmetries. is divergence free, but unlike usual scalar potential expansion, nonzero curl representing currents distributed within magnetosphere. includes sets coefficients, different degrees disturbance as determined range Kp values. latitude at earth separating open polar cap lines closing on day side about 5° lower than that previous theoretically models. At times high Kp, additional high-latitude extend back into tail. Near solstice, separation can be low 75° winter hemisphere. average northward component much smaller predicted theoretical models; this finding indicates important Current densities implied are order 10−9 A/m² across magnetotail.